Get 99,999,999 CP
Go to the blacksmith and select Upgrade. Choose an upgrade that costs exactly as much CP as you currently have, so that if you bought it you'd have 0 CP left. Then press up on the control pad, and the game will let you buy one more copy than you can afford. Make sure you have enough materials. After you make the purchase, your CP value will go into the negative, and the game corrects this by giving you exactly 99,999,999 CP. Note that an easy way to get your CP to the right number is to do Roam the World repeatedly until you come back with a CP value that ends with a 0. Then fuse atmaliths (which normally cost high even numbers) to get your CP down, or buy some non-custom abilities. Make sure you calculate how much CP you'll need to do the glitch before you start reducing your CP.
Quicky unlock mastery quest for any class
To easily unlock the mastery quests for any class, Just enter that class and roam the world and then re-enter the town.No need to fight anything, just leave and then choose to return to Libertas. This counts as a completed quest and do this 10 times and you will unlock the mastery quests.